U.S. Pat. No. 4,186,194, issued Jan. 29, 1980, discloses water soluble agents which are said to be immunological adjuvants for stimulating in the host the immune response to various antigens. The compounds comprise an acetyl or glycolyl muramic acid group, and a short peptide chain linked thereto, the first amino acid of the peptide chain being alanine, serine or glycine and the second amino acid of the peptide chain being glutamic acid or aspartic acid.